I’m sure it would be like the Comey firing, with Maguire drafting a letter laying out the case for his firing and Trump dropping the hammer. Or, he might be given the opportunity to resign. Either way, Trump will need some cover. Of course, also like the Comey firing, this will be another case of “obstruction of justice” that the Dems will want to impeach him over.
That's going to wear thin on the public, and as you point out, there will be letters that justify the terminations.
Fallout from firing an IG is peanuts compared with firing FBI Director!
Funny thing, both are getting fired for getting way out of their lane.